Automatic control valve for compressors



. dome is another check valve ll.

Patented June 10, 1941 AUTOMATIC coN'mor. VALVE Fort comanssoas Burns Dick, Ferguson, Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware Application July 15, 1938, Serial No. 219,316

Claims.

My invention relates to fluid compressors and more particularly to a valve mechanism for unloading the compressor.

One of the objects of my invention is to produce an improved valve mechanism which will automatically shut off the intake of a fluid compressor when the fluid pressure in the receiver or pressure tank of the compressor is a predetermined value.

Another object of my invention is to construct a shutoff valve of the type referred to which will be quick acting to close the compressor intake when it is operated by a predetermined maximum pressure in the receiver and which will also move to a full open position when the receiver pressure acting thereon falls to a predetermined minimum pressure and then maintain such position until the maximum pressure is again reached.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawing in which Figure 1 is a partial cross-sectional view of a compressor and a receiver having associated therewith my improved shut-off valve mechanism; Figure 2 is a longitudinal crosssectional view of the valve; and Figure 3 is an end view of the valve mechanism taken on the line 33 of Figure l. I

Referring to the drawing in detail, the air compressor I, with which I have illustrated my shut-oi! valve mechanism as being associated, is of the rotary type having a stator 2 and an eccentrically mounted rotor "3 provided with a plurality of blades 4 (one only being shown). The stator has an intake port 5 and an outlet port 6, the latter opening into an ofl dome l which is connected to a receiver or pressure tank I by means of a conduit 9. The outlet of the compressor has associated therewith a check valve ID for preventing back flow of compressed fluid. Also associated with the outlet of the The receiver 8 is adapted to be connected by the conduit I2 to any fluid pressure-actuated system, as for example, a fluid pressure-actuated braking sys-- tem. In compressors of the type described, which are of well-known construction, it is deslrable to prevent the compressor from compressing fluid after the fluid in the receiver has been placed under a predetermined maximum pressure. This is best accomplished by shutting oi! the intake port so that the air or other fluid which is being compressed by the compressor is not permitted to enter the compressing chamber. It is also desirable that the intake port not only be automatically closed at the time the fluid in the receiver reaches its maximum pressure but to also be automatically reopened when by means of a conduit H with conduit 9 leading to the receiver in order that it can be controlled by the receiver pressure. The valve mechanism, shown in detail in Figure 2, comprises a casing l5 having an attaching flange l5 for mounting it on the compressor. The casing is formed with a cylindrical bore it which communicates with the compressor intake port by a passage I l and with the atmosphere by a passage Hi, this latter passage having associated therewith a suitable air cleaner I9 for cleaning the incoming air. Within the bore I5 is a slidable valve member 20 in the form of a piston which snugly fits the bore and when in one position-closes off communication between passages l1 and i8 and in another position permits communication between these passages. The forward end of valve member 20 carries a member 2| provided with an annular rib 22 which is adapted to cooperate with a seat 23 of rubber or other suitable material mounted in the end wall of the casing. The member 20 is normally biased by a spring 24 to a position where the passages I1 and I! will be in communication with each other and rib 22 will be flrmly seated against seat 23. The valve member has associated therewith a suitable packing cup 25 'for' sealing the chamber ahead of the member and this chamber communicates with the receiver by conduit I previously referred to.

The valve member 20 is provided with a bore 26 which communicates with a small bleed pas- .sage 2! connecting the bore with the space or chamber at the forward end of the valve mem bet and lying within the outlines of rib 22 when said rib engages its seat. The bore 28 receives a rod 2| having a groove 28' and a conical end 2!, the latter of which is adapted to cooperate with a seat 30 at the juncture of the bore and ceive a nut .32 for engagement by the end. of the spring 24, thereby permitting the tension of the spring to be adjusted.

The normal position of the parts is as shown in Figure 2 where spring 24' biases valve member 20 to the right end of the casing and maintains the annular rib 22 tightly engaged with seat 23. Under these conditions, passage i8 is in communication with passage I! and the intake port of the compressor. Air can now be drawn into the compressor through the intake port and after being compressed, it is forced out through outlet 6, dome i, and through conduit 9 to the receiver. When the pressure of the fluid in the receiver reaches a predetermined value,- say for example one hundred pounds per square inch,

suflicient pressure will be developed in the chamber of the casing ahead or valve M3 to move the valve member against spring 2%, it being assumed that the spring is so adjusted that the one hundred pounds pressure acting upon the exposedpart of the valve member will be sufficient to move said member. As soon as'the valve member begins to move to the left against the spring, annular rib 22 will be moved away from seat 23. This will result in an additional area being exposed to the one hundred pounds per square inch pressure in the forward end of the valve casing and thus a. greater force will be available to move the valve member to the left to its closed position. This increased area exposed to the fluid pressure will easily compress the spring and thus cause a very rapid movement of the piston after it has once started to move, When the valve member has moved to a position where passage ll is closed, the conical end 29 of rod 28 willengage seat 30, thereby also closing the bleed passage 21 and preventing fluid under pressure from leaking through the bleed passage and groove 28' and causing a drop in pressure of the fluid in the receiver.

When the fluid pressure in the receiver has dropped to ,a predetermined minimum value,

7 say 'for example eighty-five pounds per square inch, spring 24 will then be eflective to move valve member 20 to the right and again place passage ii in communication with passage in. When the valve member reaches its extreme right-hand position, the annular rib 22 will again engage seat 23 and any fluid under pressure which may be trapped in the space enclosed by the annular rib will bleed ofi through the passage 21 and groove 28, thus insuring that the valve member will again be positively held in its right-hand position and that the fluid in the chamber ahead of the valve member will not be effective on the surface surrounded by the rib. If thebleed passage were not present,

' air under pressure would be trapped at the forward end of the valve member enclosed by the rib, thereby preventing the rib from tightly engaging seat 23.

From the foregoing, it is apparent that I have designed a shut ofi valve which will be quick acting in its closing movement and one in which the valve member is insured of being held in its open position after it is moved to such position by ,the action of the spring and ass. result of adrop in pressure of the fluid in' the; receiver. If the valve member had only a uniiormarea exposed to the receiver pressure at all times, the valve member would not be quickly moved to closed position and as a result, the compressor would be unloaded by a slow closing of the intake passage which would cause a prolonged period of compressor operation.

Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what .I claim as new and desire to secure by Letters ing a portion of the movable member and the casing for forming a chamber which is adapted to be connected to the fluid pressure receiver, means comprising another portion of the mov able member for forming a second chamber,- means for connecting the second chamber to the first chamber when said movable member is initially moved toward a position closing the port and against the spring by a predetermined fluid pressure, means forming a bleed passage from the second chamber, and valve means controlled by movement of the movable member for closing said bleed passage when the movable member is in a position closing the port.

2. In valve mechanism ofthe class described for association with an intake of a compressor and the fluid pressure receiver therefor, a casing having a port for communication with the compressor intake, 9. single movable member for closing the port, a spring for biasing the member to open position, means comprising a portion of the movable member and the casing for forming achamber which is adapted to be connected to the fluid pressure receiver, means including a. relief passage through the movable member for connecting the chamber to atmosphere, and means controlled by movement 0! the movable member to port closed position for closing said passage whereby the pressure from the receiver will be eflective to maintain the member in port closed position.

3. In valve mec of the class described for association withan intake of a compressor and the fluid pressure receiver therefor, 2 casing having a port for communication with the compressor intake, a single movable member for closing the port, a spring for biasing the memher to open position,means comprising a portion of the movable member and the casing for forming a chamber which is adapted to be connected to the fluid pressure receiver, means including a relief passage through the movable member for connecting the chamber to atmosphere, and valve means comprising a fixed ele-' ment and a valve seat on the movable member for controlling said passage, said valve means being caused to assume a closed position when the movable member is moved to port closed position and to be opened when the pressure in the chamber is such as to permit the spring to move the member to port open position.

4. In valve mechanism of the class described for association with a fluid compressor and a receiver therefon-a valve casing provided with a cylinder having an inlet thereto'and an outlet a piston slidable in said cylinder for cutting oi! the outlet from the inlet. said piston and a portion of the cylinder forming a chamber adapted to be connected to the receiver, a central projection on said piston, cooperating means on said projection land the end wall of the cylinder for preventing the end suriace of 'said projection from being exposed to fluid under pressure inthechamber, a spring for biasing said piston to a position where the outlet is in communica tion with the inlet and the cooperating means are in operative position, said piston being moved against said biasing spring by a predetermined pressure in said chamber and initial movement of said piston causing said cooperating means to become inoperative and thus permit the end surface of the projection tobe acted upon by said predetermined pressure, means forming a bleed passage through the piston and theprojection, and a fixed member for closing said bleed passage when the piston is moved to a position cutting oil communicationbetween the inlet and outlet.

5. In valve mechanism of the class described for association with a fluid compressor and a receiver therefor, a valve casing provided with a cylinder having an inlet thereto and an outlet for connection with the intake of the compressor, a piston slidable in said cylinder for closing the outlet, said piston and a portion of the cylinder forming a chamber adapted to be connected to the receiver, an annular rib on they end (I said piston, a seat for the rib carried by the end wall or the cylinder, means forming a bleed passage through the piston and connected with the space surrounded by the rib. a valve for said passage comprising a stationary valve element and a valve seat carried by the piston, said valve element and seat being so associated with each other that the valve is closed only when the piston is in a position to close the .outlet, and a spring for biasing said piston to a position where the outlet is open and the rib on the piston engages its seat.

7 swans mcx. 

